The present invention relates to an improved railway car brake shoe and particularly to an adaptive brake shoe configuration that accommodates brake rigging misalignment such that substantially no loss of braking efficiency occurs and the potential for undesirable heating of localized portions of the car wheel is minimized.
Mis-alignment of brake rigging on railway cars can occur due to bent rigging components, the dirty environment in which the brake rigging components are required to operate, poorly designed brake rigging, and track curvature.
This mis-alignment of brake rigging is detrimental, since one brake shoe carried by a given brake beam overrides the wheel flange, while the other brake shoe rides off the wheel rim. In the first instance, interference between the brake shoe and wheel flange prevents the brake shoe friction face from engaging the wheel tread, so that loss of braking occurs at that wheel. In the latter instance, a groove wears in the brake shoe face, which also affects the ability of the brake shoe to fully engage the wheel tread, when the brake rigging subsequently becomes aligned. In addition to the decreased braking efficiency resulting from mis-aligned brake rigging and consequent shifting of the brake shoe relative to the wheel/axle units, engagement of the brake shoe with the wheel flange can further generate high levels of heat in the wheel flange and accordingly a high temperature gradient across the wheel. This is believed to contribute to structural damage to the wheel, which ultimately represents a high cost to the railroads for wheel replacements.